With the development of technology, the application of projector becomes more and more diverse and the installation of projector is not limited to horizontal installation (i.e., table top or ceiling mount). A projector needs a vertical installation when upward projection or downward projection is required; or, a projector needs a portrait installation (or portrait mode) if beam-up or beam-down is required. For a projector using a high pressure mercury lamp as a light source, in order to maintain a certain lamp life, the projector has different cooling ways for lamp in response to the horizontal installation, vertical installation or portrait installation. Because of the projector has different cooling conditions in response to the horizontal installation, vertical installation or portrait installation, an improper installation may lead to a poor cooling effect if there is a need to switch the projection angle; and consequently, the usage life of the lamp may be significantly reduced. Therefore, to solve the aforementioned problems, it is quite important for the persons in the art to develop a projector for an occasion requiring switching the projection angles frequently.
The information disclosed in this “BACKGROUND OF THE INVENTION” section is only for enhancement understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Furthermore, the information disclosed in this “BACKGROUND OF THE INVENTION” section does not mean that one or more problems to be solved by one or more embodiments of the invention were acknowledged by a person of ordinary skill in the art.